The border-block-start-width CSS property defines the width of the logical block-start border of an element, which maps to a physical border width depending on the element's writing mode, directionality, and text orientation. It corresponds to the border-top-width, border-right-width, border-bottom-width, or border-left-width property depending on the values defined for writing-mode, direction, and text-orientation.

/* <'border-width'> values */ border-block-start-width: 5px; border-block-start-width: thick;  /* Global values */ border-block-start-width: inherit; border-block-start-width: initial; border-block-start-width: revert; border-block-start-width: unset; 

border-block-start-width

The border-block-start-width CSS property defines the width of the logical block-start border of an element, which maps to a physical border width depending on the element's writing mode, directionality, and text orientation. It corresponds to the border-top-width, border-right-width, border-bottom-width, or border-left-width property depending on the values defined for writing-mode, direction, and text-orientation.

Syntax

/* <'border-width'> values */ border-block-start-width: 5px; border-block-start-width: thick;  /* Global values */ border-block-start-width: inherit; border-block-start-width: initial; border-block-start-width: revert; border-block-start-width: unset; 

Related properties are border-block-end-width, border-inline-start-width, and border-inline-end-width, which define the other border widths of the element.

Initial value	medium
Applies to	all elements
Inherited	no
Percentages	logical-width of containing block
Computed value	absolute length; 0 if the border style is none or hidden
Animation type	a length

Values

<'border-width'>

The width of the border. See border-width.

Formal definition

Initial value	medium
Applies to	all elements
Inherited	no
Percentages	logical-width of containing block
Computed value	absolute length; 0 if the border style is none or hidden
Animation type	a length

Formal syntax

<'border-top-width'>

Examples

Border width with vertical text

HTML

<div>   <p class="exampleText">Example text</p> </div> 

CSS

div {   background-color: yellow;   width: 120px;   height: 120px; }  .exampleText {   writing-mode: vertical-lr;   border: 1px solid blue;   border-block-start-width: 5px; } 

Results

Specifications

Specification
CSS Logical Properties and Values Level 1 # border-width

See also

This property maps to one of the physical border properties: border-top-width, border-right-width, border-bottom-width, and border-left-width writing-mode, direction, text-orientation Select your preferred language English (US)EspañolFrançais日本語 Change language